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THX-1138

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Everything posted by THX-1138

  1. Thanks! Now, it's probably difficult to remove the impurities (ferrous and cupric chlorides) from the bath, so for disposal I should probably neutralise it with NaOH until the pH is at or above 7.0, correct? What will be the result? Aqueous NaCl and precipitated elemental iron and copper?
  2. So let's see: [ce] 2FeCl3 + Fe -> 3FeCl2 [/ce] [ce] FeCl3 + Cu -> FeCl2 + CuCl [/ce] Is this probably what's happening here?
  3. Really! I've always thought copper was more reactive. No basis in anything except impressions gained. So I'm guessing that the steel got turned into ferrous chloride in solution. Bugger. /me tries to figure out the reaction formulae. Hmm, I'm not getting it.
  4. Over the last few days, I had an AP (armour-piercing) bullet in a ferric chloride etchant bath to remove the copper jacket. Which it did, but to my surprise some of the underlying penetrator was attacked as well. AFAIK, these are hardened steel, so I wouldn't have expected the iron(III) chloride to have affected it. Was my expectation incorrect? Will ferric chloride attack iron and steel items as well? Thanks! Merged post follows: Consecutive posts mergedWas this a stupid question?
  5. Semi-facetious: Is that also why electrical discharges are blue? (Where nothing's being volatised..)
  6. Yes. In addition to looking for it under 'spirits of salts' and 'muriatic acid,' you can probably find it at any store that sells swimming-pool maintenance supplies.
  7. I'd like to finish up learning Ruby, Python, and Java first. Then.. I don't know, maybe Lua.
  8. Before settling into a final approach, I very strongly recommend that you do some research.. because obvious (and some not-so-obvious) watermarking techniques are covered by patents. The last thing you want is to end your project with an 'A' and an infringement lawsuit. Otherwise, a non-infringing, open, high-quality watermarking mechanism would be a tremendous boon to the world, so good luck!
  9. Nope. Nowadays they store a 'factory reinstall' feature in a separate partition. Typically using that wipes the entire drive, though. IMHO, the reinstall partition itself typically gets deliberately wiped by any sensible person installing Linux.
  10. Are these trick questions? Assuming not and taking the brute-force approach, 4. (30 + 20 + 10) * 107 = 6 * 1010 bytes 5. 1910 = 100112, so 5 bits per character ought to do it. You'd even have room to represent 12 additional characters.
  11. I'm thinking about 17-25cm, and with tips that can get a grip on odd shapes. What's a good non-reactive coating? Nickel? Teflon®? Maybe plastic 'tweezers' would do, if they're high-temp tolerant.. or hemostats..?
  12. I need some forceps or tongs that I can use to extract items from caustic solutions. E.g., pulling a circuit board from a etching solution, or something from an HCl bath. They need to be pretty long, easily manipulated (i.e., closed and held closed) far from the tip, heat-tolerant, and reasonably non-reactive. Any suggestions of what I can use and where I can get one? Thanks!
  13. I'm thinking about cooling a non-flat surface; specifically a cylinder. The item in question gets too hot for simple air-based heat-sinking to be sufficient, so I'm toying with the idea of using a Peltier device to force-cool it. However, all the Peltier thermocooling units I've seen are essentially wafers. Are they ever found in other shapes? How simple would it be for me to construct one? (The materials, I mean, not the matter of machining it.) Thanks..
  14. I asked in another forum and my mistakes were pointed out to me. Among other things, the substrate needs to be connected to the drain node. Thanks!
  15. Try this graphically. I changed the source resistor to 1 ohm and plotted the input voltage against the drain voltage -- so the drain-source path makes the negative half of a voltage divider with R1. Shouldn't the drain voltage have dropped quickly to near zero, indicating RDS dropping likewise?
  16. YT: More complicated than it needs to be? Sure! I have a need, yes, but I'm using it as a learning experience, fiddling with new things. Once I have something that works (and that I understand ), I'll pare it back to the basics I need. As it is, though, I haven't used SPICE in a quarter of a century, and then not in this way. And I've never used FETs in my hobby projects. Okey, trying an ideal circuit: SPICE's generic N-channel MOSFET; supply voltage 20VDC; 1Mohm resistances at drain, gate, and source; input voltage (across gate and ground) from -20 to +20 by 0.5V steps. I'm attaching the circuit, the SPICE layout, and the SPICE results. That surely doesn't look like a fast turn-on to me. What am I doing wrong? mosfet.pdf mosfet-spice-input.txt mosfet-spice-output.txt
  17. I haven't gone beyond modeling in SPICE (i.e., no actual wiring yet), and I'm probably doing something wrong, but I can't get switching behaviour out of MOSFETs at low voltages (5-12VDC). Just gradual low-gain changes, which certainly won't serve for a low-resistance path to anything. Of course, maybe the models I'm using are bogus, since SPICE seems to think the MOSFET gate is a current sink deep enough to drop the comparator high-level output voltage significantly unless I include a 10M resistance between them. There's an excellent chance I haven't a clew at all, too. But it's all about learning anyway..
  18. What's the best way to model a meter in SPICE, anyway?
  19. Probably not the right forum; perhaps 'experiments' or 'projects' would be better, but.. I'm noodling up a variable-voltage power supply (~0-35VDC), and I'm using a Radio Shack 1mA FSV 15V panel meter to display the output. (15Kohms feed resistor to get the appropriate voltage drop.) Since the voltage range of the supply goes to about double that, I thought I'd put in a switch to make the appropriate changes to the circuit to allow the meter to display 0-30VDC, and add the notations to the meter face. I want to put a shunt across the meter to keep from damaging it in an over-voltage situation, and also give an indication of the fact with an LED. Currently I'm simulating this and using a 16V Zener (to go a wee bit off the scale) and an LM339 comparator. To half-scale the meter is simplicity itself; just switch in an additional 15K resistor to its input path. And adjusting the shunt appropriately could be done essentially by changing the Zener diode. However, I'd like to stick with just one Zener, since the voltage drop across the meter, with its 15K resistor, will still be 15V. I haven't done a lot with Zeners in the past, and I'm not completely conversant with all their behaviours. In other words, I'm having trouble figuring out a circuit that will use a 16V Zener to indicate overvoltage in both full-scale (15V) and half-scale (30V) situations. Also, one that doesn't go all wonky when the low-impedance meter gets added to the circuit! I've tried some isolation diodes, but no joy. Just not doing it right, I guess. I'm attaching a PDF showing the current circuit with which I'm playing, including a SPICE input deck. In the PDF, the highlighted areas on the schematic and netlist show what breaks the results: if the meter isn't connected, all's well; if it is, the break point drops from 16V to less than 1V. Since this is essentially play and a learning exercise for me, I'm interested in any constructive feedback. Thanks! MeterShunt.pdf
  20. I have been given a quantity of TO-92 transistors with the National Semiconductor brand on them. However, I cannot identify them. When I asked National, they told me they sold their discrete line to Fairchild in 1997. The Fairchild Web site isn't very tech-question friendly, and singularly bereft of eddresses, so I'm going to ask here in a better hope of getting an answer. There are two types; all have colour codes on the back: 427 A05 yellow-red-purple 333 A05 silver-silver-silver Anyone have any inkling? Only three colour bands doesn't sound particularly useful, but.. Thanks!
  21. FWIW, I finally dug out one of my salvaged water-heater anodes and turned down a segment to show how much viable magnesium it had. It seems to actually be fairly pure; the curls and swarf from turning it ignite very nicely.
  22. Um, yeah, that much is kinda obvious. But to what radius do you soften the point of penetration; should the wire be heated (and to what degree) as well; how do you assure the glass will adhere to the wire; etc..
  23. I picked up some odd glassware at a surplus place -- about 50ml, but with no bottom -- and I'd like to try turning one of them into a Jacob's ladder column. The challenge is how to pass the wire through the (flint) glass wall of the bottle for an external connexion. How does one pass a wire through a glass interface, keeping a good seal? Like a connector passing out of the bottom of an old television valve? Thanks!
  24. Since it relates explicitly to SVG, I also asked this question i the SVG developers group on Yahoo!. Someone replied there, and I'm copying the response here for completeness and eddy-fication of anyone wandering by this topic in the future. From Frank Bruder: I'm not sure I agree that it's "quite simple," but there it is.
  25. I never studied the curve algorithms; I just use 'em. So I really have no idea how to answer this question. Once again working in SVG. When using the cubic Bézier curve commands, I want to find out the coordinates of the actual peaks. For instance, c 3.75,20.0 5.00,-20.00 8.75,0.00 approximates (!) a one-cycle sine curve. I want to be able to figure out the curve's minimum and maximum (y-axis) values. How can I do this? Thanks!
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